Re-Using Yeast (what's the science)?

[RukusDM]

Well I've read that picking top and bottom as you referenced is bad. What I've done more specificly is to scrape out yeast sludge mix from the bottom and put it in a sanitized container then add the distilled sanitized water and do the successive washes from that not targeting just yeast.

Its a slightly different take on the yeast wash where you just add several quarts of water and slosh around and wait to settle and then decant yeasts.

I'm sure the current methods work well, I just wanted to produce a cleaner environment for yeast storage. The less total sugars suspended in liquid would seem to be a better thing as those are what contribute to spoilage and bacteria cultures to grow.

I don't have any real science that pushed me to try this other than trying to remove as much sugar from the storage medium as possible before long term storage.

I would assume if there are no sugars for food then bacteria would have a hard time taking over even if you had some in the stored yeast. I would assume they would also become dormant or die.

Again, not based on any real science, but more on feel and very basic understanding of bacteria.

 

[pkeeler]

If you wanted to use a clean yeast for every brew, you could get some WY 1056 or WY 1272 and, like Papazain, use it over and over. I've made starters from the dregs of previous batch bottles.

Slants, sterilization, etc. are just factors of safety. Each one adds additional insurance against yeast changes (mutations, genetic drift) and bacterial infection. However, each comes with a cost (in time and/or money). Same with buying a new smack pack with every brew, it adds up. However, if you want a different yeast, you are going to have to buy it. The only way Wyeast can stay in business is to offer all these different yeasts because you have an entire store of free yeast in your basement or refrigerator. Are they really all that different though? That is for another thread LOL

Personally, I like to spend about $.75-1 per brew on yeast. So, that means I buy a smack pack, make a beer, wash the primary cake into 6 ball jars (7 oz), refrigerate them until I use them. Now, I'm not that meticulous about sanitizing and I can't guarantee the genetic purity of the strain (no slant system or microscope). But it works for me, probably because I'm putting so much slurry into each ball jar. I could have made 12 jars with less slurry, but I would think the lower amounts of yeast in each jar increases my risk of something going wrong (but I have no idea what those percentages are really). Now, I could probably take each of those 6 and make another generation and get my beer cost for yeast to $0.15. But I would have to worry more about sanitation and genetic drift of the original batch. Plus, I'd have to get another fridge to hold all these ball jars ;-) Oh, and I like trying new yeast, and would never make 36 in a row with the same yeast!

Now, as to washing vs. leaving the cake. If the cake is under beer and the fermenter is filled with CO2, you could probably leave it. Probably how beer was made for millenia (beer racked off, new beer racked on). However, personally, I'd hate to have my next beer dissolve that crap off the sides of the fermenter. It is hard to wash the fermenter and leave behind the yeast cake.

As for leaving beer in the primary for 4-6 weeks. Seems like people get away with it. However, yeast washing seems to me to be one of those times where moving the beer to a secondary makes sense. I like to harvest yeast fresh, maybe 1 week from pitching. But I don't know if it makes any difference; and I don't care to get involved in the "Primary Only" religious crusade that is happening around here.

 

[COLObrewer]

A ton of good information here, I'm glad to see so many people with so many questions, that's how we learn.

A couple of things I thought about while reading through this thread:

1. Regarding collection of yeast to re-use; I believe the conical fermentors (at least the large commercial ones) have a valve allowing them to extract yeast from the middle of the cake in order to select the best cross section of yeast for maintenance and propagation. I'm not sure how well this works since "all trubs does not an ideal sample make". It's just an observation, I probably read it somewhere.

I'm curious about those commercial breweries with flat bottom fermentors, do they have a valve that collects from a certain height in the vessel? Do they all do this? I imagine they could pump it from the level they want with an adjustable pipe coming from the top also?

2. I have been curious for some time regarding all the talk of infection, it seems to be a growing concern, maybe it's just tracking with a growing number of new brewers. I have gotten infections but they have been only in beers that I have had "open" for extended periods of time in my cellar. So far these have been good infections, (Knock on brett infected wood).

I am convinced now that most infections come from the practice of brewing where we eat, clean, prepare food. As studies have shown the place where the greatest number of bacterium reside in the home is the kitchen, (I wouldn't brew in the bathroom though). This is because of the great need for sanitation in this hobby, we want to be close to the source of water, cleaning supplies etc. Or maybe it is WHY we need sanitation so much?

Personally I mostly brew outside, or in the shop, it makes things cumbersome because of all the carrying, hoses, etc. I was contemplating installing a wash tub in the shop for this reason but now I'm not so sure that this is the main reason We've not had a problem with infection. I'm not the most sanitary person brewing to be sure and lately I seem to be flirting with unsanitary procedures wondering each time if this is the practice that will get me an infection.

I'm wondering what the ratio of infection is for someone that brews outside or away from the kitchen, compared to someone that always brews in the kitchen?

Sorry for my rambling, brew on my friends

 

[MalFet]

Personally I mostly brew outside, or in the shop, it makes things cumbersome because of all the carrying, hoses, etc. I was contemplating installing a wash tub in the shop for this reason but now I'm not so sure that this is the main reason We've not had a problem with infection. I'm not the most sanitary person brewing to be sure and lately I seem to be flirting with unsanitary procedures wondering each time if this is the practice that will get me an infection.

I'm wondering what the ratio of infection is for someone that brews outside or away from the kitchen is, compared to someone that always brews in the kitchen?

Based on other (mostly-unrelated) work I do, I suspect it's a bit of a trade-off. Kitchens are chock full of lacto, pedio, and aceto, but the outside is full of mold and wild yeast. My bigger concern with shifting everything outside would be air movement. If you are in a well protected area (like your shop, perhaps) it might be a moot point, but rapid air movement transports dust, and dust is like the spaceship that gets infections all up in your junk.

Don't get me wrong, I don't think that brewing outside -> infections. Your wort is hot enough to manage that, and a nice big yeast pitch stacks the deck in favor of the good guys. I think sanitation for brewing is relatively straightforward -- not that we haven't all had bad luck once or twice -- and that it is perfectly possible to brew inside our out infection free.

I certainly wouldn't plate yeast outside, though. A lot of the protective measures involved in yeast culturing involve manipulating air currents to keep dust away from your samples. Outside, that wouldn't be possible to control.